SEED PROTEIN PROFILES IN THE NARROW-LEAVED SPECIES OF CHENOPODIUM OF THE WESTERN UNITED STATES: TAXONOMIC VALUE AND COMPARISON WITH DISTRIBUTION OF FLAVONOID COMPOUNDS

Water soluble seed proteins from 69 populations representing seven species of Chenopodium were separated electrophoretically. Very little or no intraspecific variation was detected. The use of seed proteins as taxonomic characters was evaluated and compared to data from flavonoid chemistry. Seed proteins are of value in distinguishing C. atrovirens and C. leptophyllum, something which could not be done with flavonoids. Proteins and flavonoid data demonstrated that C. hians and C. leptophyllum are distinct. An analysis of storage proteins failed to differentiate C. desiccatum from C. atrovirens and C. pratericola even though the species are distinct in flavonoids and other characters. Chenopodium atrovirens and C. pratericola produce similar or identical seed proteins, just as they are identical in flavonoids. Seed proteins indicated that plants referable to C. incognitum represent two biological entities, one apparently a minor morphological variant of C. atrovirens and the other conspecific with C. hians. The same interpretation had been given on the basis of flavonoid chemistry. The protein data suggest a close relationship between C. subglabrum on the one hand and C. atrovirens and/or C. desiccatum on the other.     

COMPARISON OF ISOZYMES AMONG TYPHA SPECIES IN THE EASTERN UNITED STATES

Biochemical phenotsypes of four taxa of Typha from the eastern United States were determined by starch gel electrophoresis. The isozyme banding patterns of T. latifolia, T. angustifolia and T. domingensis are distinct and allow unambiguous species identification when morphological characters are inadequate or unsuitable. The fourth form, T. glauca, is not an F₁ hybrid, but it does appear to be intermediate between T. latifolia and T. angustifolia. The status of T. glauca and evolutionary relationships among the four forms may now be clarified by additional sampling because of the distinct and relatively invariant isozyme banding patterns which are described.     

PATTERNS OF ALLOZYME VARIATION IN DIPLOID AND TETRAPLOID CENTAUREA JACEA AT DIFFERENT SPATIAL SCALES

Abstract.— The extent and spatial patterns of genetic variation at allozyme markers were investigated within and between diploid and autotetraploid knapweeds (Centaurea jacea L. sensu lato, Asteraceae) at contrasted geographic scales: (1) among populations sampled from a diploid‐tetraploid contact zone in the northeastern part of the Belgian Ardennes, and (2) within mixed populations from that zone where diploids and tetraploids coexist. Our data were also compared with a published dataset by Sommer (1990) describing allozyme variation in separate diploid and tetraploid knapweeds populations collected throughout Europe. Genetic diversity was higher in tetraploids. In the Belgian Ardennes and within the mixed populations, both cytotypes had similar levels of spatial genetic structure, they were genetically differentiated, and their distributions of allele frequencies were not spatially correlated. In contrast, at the European scale, diploids and tetraploids did not show differentiated gene pools and presented a strong correlation between their patterns of spatial genetic variation. Numerical simulations showed that the striking difference in patterns observed at small and large geographic scales could be accounted for by a combination of (1) isolation by distance within cytotypes; and (2) partial reproductive barriers between cytotypes and/or recurrent formation of tetraploids. We suggest that this may explain the difficulty of the taxonomic treatment of knapweeds and of polyploid complexes in general.     

THE CONTRIBUTION OF MATING SYSTEM VARIATION TO REPRODUCTIVE ISOLATION IN TWO CLOSELY RELATED CENTAURIUM SPECIES (GENTIANACEAE) WITH A GENERALIZED FLOWER MORPHOLOGY

In closely related plant species that display strong similarities in phenology and pollinator communities, differences in breeding system and associated shifts in floral traits may have important effects on the magnitude and direction of heterospecific pollen flow and hybridization. Here, we quantified the strength of several pre‐ and postzygotic barriers acting between the facultatively outcrossing Centaurium erythraea and the predominantly selfing C. littorale via a suite of experiments, and estimated the frequency of hybridization in the field using molecular markers. The reproductive barriers primarily responsible for preventing hybridization were essentially prezygotic and these acted asymmetrically. Due to differences in floral display, pollen production, and pollen transfer rates, heterospecific pollen flow occurred predominantly from C. erythraea to C. littorale. In C. littorale, on the other hand, close anther–stigma positioning and resulting higher capacity for autonomous selfing functioned as an efficient barrier to counterbalance the higher risk for hybrid mating. In both species the action of all reproductive barriers resulted in a small opportunity for hybrid establishment, which was confirmed by the occurrence of only ～1% putative hybrids in the field. Our findings confirm that differences in breeding system affect heterospecific pollen transfer patterns and that autonomous selfing may efficiently prevent hybridization.     

A QUANTITATIVE STUDY OF VARIATION IN THE CHENOPODIUM ATROVIRENS-DESICCATUM-PRATERICOLA COMPLEX

Multivariate analyses were applied to 96 populations (OTUs) of plants, traditionally referred to Chenopodium atrovirens, C. desiccatum, and C. pratericola, in an attempt to evaluate the numerous and often contradictory taxonomic treatments of plants in this complex. The study consisted of two major parts. The first involved the use of cluster and principal components analyses using 14 morphological characters on the entire set of 96 OTUs to search for phenetically distinct groupings; these analyses were conducted without knowledge of traditional taxonomic designations of individual OTUs. Three reasonably well-defined groups emerged from these preliminary analyses. When traditional taxonomic designations were applied to member OTUs of each group, one group was composed primarily of C. atrovirens, another of C. pratericola and the third of C. desiccatum. The second part of the study utilized canonical analysis to: 1) confirm the integrity of the phenetic groups, 2) to classify OTUs difficult to identify to species using traditional methods, and 3) to provide an evaluation of characters important in the separation of these groups. This analysis confirmed the integrity of the groups and provided a classification to species of nearly all of the otherwise difficult OTUs. In addition, canonical analysis demonstrated that a combination of characters was important in the separation of the phenetic groups.     

RACES OF PERONOSPORA MANSHURICA IN THE UNITED STATES

I propose a set of 11 soybean varieties for the differentiation of races of Peronospora manshurica: Pridesoy, Norchief, Mukden, Richland, Roanoke, Illini, S 100, Palmetto, Dorman, Kabott, and Ogden. When I employed these, I found fifteen new races of Peronospora manshurica, the casual agent of downy mildew of soybeans, described them, and assigned numbers 9 through 23. Race 8 was encountered most frequently and occurred at 40% of the locations from which seed samples were obtained. Races 1, 2, 10, 12, 18, and 23 occurred at 5–8% of the locations sampled. Race 10 was common in the southern U. S. Of 247 soybean seed lots sampled, 73% contained some oospore-encrusted seeds. These ranged from 12–26% lighter than healthy seeds. The percentage of oospore-encrusted seeds occurring in seed lots ranged from 0–25%.     

CHROMOSOME NUMBERS IN THE LEGUMINOSAE. III. SPECIES OF THE SOUTHWESTERN UNITED STATES AND MEXICO

Turner, B. L., and Olin S. Fearing. (U. Texas, Austin.) Chromosome numbers in the Leguminosae. III. Species of the Southwestern United States and Mexico. Amer. Jour. Bot. 47(7) : 603–608. Illus. 1960.—Chromosome counts for 43 species of the Leguminosae from the southwestern United States and Mexico have been reported. These include first reports for 42 taxa of which 16 are for the subfamily Mimosoideae. Olneya tesota (2n = 18) is the only new generic count listed. Chromosome reports of particular significance include a single polyploid count for a North American species of Acacia, as well as diploid and tetraploid counts for closely related taxa in this genus. Four species of the genus Schrankia were found to be diploid with In = 26, indicating a base of x = 13 instead of the x = 8 reported by some previous workers. Leucaena pulverulenta was found to have a diploid count of 2n = 56 indicating a base of x = 14.